Integrated Detector Assemblies for a Wearable Module of an Optical Measurement System

ABSTRACT

An optical measurement system includes a wearable module having at least one time-resolved single photon photodetector configured to detect photons from at least one light pulse after the at least one light pulse is scattered by a target within a body of a user; at least one light guide configured to receive the photons and guide the photons to the at least one photodetector; and a housing that houses both the at least one photodetector and at least a portion of the at least one light guide. The optical measurement system further includes a signal processing circuit configured to determine a temporal distribution of the photons detected by the at least one photodetector and generate a histogram based on the temporal distribution of the photons.

RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application No. 63/038,459, filed on Jun. 12, 2020,and to U.S. Provisional Patent Application No. 62/992,555, filed on Mar.20, 2020, and to U.S. Provisional Patent Application No. 62/979,866,filed on Feb. 21, 2020. These applications are incorporated herein byreference in their respective entireties.

BACKGROUND INFORMATION

Detecting neural activity in the brain (or any other turbid medium) isuseful for medical diagnostics, imaging, neuroengineering,brain-computer interfacing, and a variety of other diagnostic andconsumer-related applications. For example, it may be desirable todetect neural activity in the brain of a user to determine if aparticular region of the brain has been impacted by reduced bloodirrigation, a hemorrhage, or any other type of damage. As anotherexample, it may be desirable to detect neural activity in the brain of auser and computationally decode the detected neural activity intocommands that can be used to control various types of consumerelectronics (e.g., by controlling a cursor on a computer screen,changing channels on a television, turning lights on, etc.).

Neural activity and other attributes of the brain may be determined orinferred by measuring responses of tissue within the brain to lightpulses. One technique to measure such responses is time-correlatedsingle-photon counting (TCSPC). Time-correlated single-photon countingdetects single photons and measures a time of arrival of the photonswith respect to a reference signal (e.g., a light source). By repeatingthe light pulses, TCSPC may accumulate a sufficient number of photonevents to statistically determine a histogram representing thedistribution of detected photons. Based on the histogram of photondistribution, the response of tissue to light pulses may be determinedin order to study the detected neural activity and/or other attributesof the brain.

A photodetector capable of detecting a single photon (i.e., a singleparticle of optical energy) is an example of a non-invasive detectorthat can be used in an optical measurement system to detect neuralactivity within the brain. An exemplary photodetector is implemented bya semiconductor-based single-photon avalanche diode (SPAD), which iscapable of capturing individual photons with very high time-of-arrivalresolution (a few tens of picoseconds).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments and are a partof the specification. The illustrated embodiments are merely examplesand do not limit the scope of the disclosure. Throughout the drawings,identical or similar reference numbers designate identical or similarelements.

FIG. 1 illustrates an exemplary optical measurement system.

FIG. 2 illustrates an exemplary detector architecture.

FIG. 3 illustrates an exemplary timing diagram for performing an opticalmeasurement operation using an optical measurement system.

FIG. 4 illustrates a graph of an exemplary temporal point spreadfunction that may be generated by an optical measurement system inresponse to a light pulse.

FIG. 5 illustrates an exemplary non-invasive wearable brain interfacesystem.

FIGS. 6A, 6B, 7A, and 7B illustrate various views of an exemplarywearable module that may be used in an optical measurement system.

FIGS. 8 and 9 illustrate cross-sectional views of the wearable module ofFIGS. 6A-7B, including an exemplary light source assembly included inthe wearable module, taken along the dash-dot-dash line labeledXIII-XIII in FIG. 7A.

FIGS. 10 and 11 illustrate cross-sectional views of the module of FIGS.6A-7B, including an exemplary detector assembly included in the wearablemodule, taken along the dashed line labeled X-X in FIG. 7A.

FIGS. 12-17 illustrate embodiments of a wearable device that includeselements of the optical detection systems described herein.

FIGS. 18 and 19 illustrate exemplary methods.

FIG. 20 illustrates an exemplary computing device.

DETAILED DESCRIPTION

Optical measurement systems and methods, and wearable modules for use inan optical measurement system, are described herein. For example, anoptical measurement system may include a wearable module and a signalprocessing circuit. A wearable module may include at least onetime-resolved single photon photodetector configured to detect photonsfrom at least one light pulse after the at least one light pulse isscattered by a target within a body of a user, at least one light guideconfigured to receive the photons and guide the photons to the at leastone photodetector, and a housing that houses both the at least onephotodetector and at least a portion of the at least one light guide.The housing is configured to support and/or house other components ofthe wearable module. A signal processing circuit may be configured todetermine a temporal distribution of the photons detected by the atleast one photodetector and generate a histogram based on the temporaldistribution of the photons. The signal processing circuit may be housedin the housing or in an additional housing separate from the housing.

The systems, methods, and apparatuses described herein provide variousbenefits and advantages compared with conventional optical measurementsystems, methods, and apparatuses. For example, by integrating adetector and a light guide into a wearable module as described herein,the path length a photon travels along the light guide to the detectoris substantially shortened relative to conventional configurations. As aresult, temporal dispersion in the detected signal may be substantiallyreduced or eliminated.

Furthermore, the configurations described herein eliminate long opticalfibers used in conventional configurations to connect a wearable moduleto a detector that is located off the module, thereby improving comfortto the user when wearing the wearable module. In conventional systems,the weight of the long optical fibers applies a torque and other forcesto the wearable module, thereby causing the wearable modules to move andthus degrading signal quality. In contrast, by not using long opticalfibers, the wearable modules described herein are not subject to suchundesirable movement. These and other advantages and benefits of thepresent systems, methods, and apparatuses are described more fullyherein and/or will be made apparent in the description herein.

FIG. 1 shows an exemplary optical measurement system 100 configured toperform an optical measurement operation with respect to a body 102.Optical measurement system 100 may, in some examples, be portable and/orwearable by a user.

In some examples, optical measurement operations performed by opticalmeasurement system 100 are associated with a time domain-based opticalmeasurement technique. Example time domain-based optical measurementtechniques include, but are not limited to, TCSPC, time domain nearinfrared spectroscopy (TD-NIRS), time domain diffusive correlationspectroscopy (TD-DCS), and time domain digital optical tomography(TD-DOT).

As shown, optical measurement system 100 includes a detector 104 thatincludes a plurality of individual photodetectors (e.g., photodetector106), a processor 108 coupled to detector 104, a light source 110, acontroller 112, and optical conduits 114 and 116 (e.g., light guides, asdescribed more fully herein). However, one or more of these componentsmay not, in certain embodiments, be considered to be a part of opticalmeasurement system 100. For example, in implementations where opticalmeasurement system 100 is wearable by a user, processor 108 and/orcontroller 112 may in some embodiments be separate from opticalmeasurement system 100 and not configured to be worn by the user.

Detector 104 may include any number of photodetectors 106 as may serve aparticular implementation, such as 2^(n) photodetectors (e.g., 256, 512,. . . , 16384, etc.), where n is an integer greater than or equal to one(e.g., 4, 5, 8, 10, 11, 14, etc.). Photodetectors 106 may be arranged inany suitable manner.

Photodetectors 106 may each be implemented by any suitable circuitconfigured to detect individual photons of light incident uponphotodetectors 106. For example, each photodetector 106 may beimplemented by a single photon avalanche diode (SPAD) circuit and/orother circuitry as may serve a particular implementation.

Processor 108 may be implemented by one or more physical processing(e.g., computing) devices. In some examples, processor 108 may executeinstructions (e.g., software) configured to perform one or more of theoperations described herein.

Light source 110 may be implemented by any suitable component configuredto generate and emit light. For example, light source 110 may beimplemented by one or more laser diodes configured to emit light in oneor more discrete wavelengths or narrow wavelength bands. In someexamples, the light emitted by light source 110 is high coherence light(e.g., light that has a coherence length of at least 5 centimeters) at apredetermined center wavelength. In some examples, the light emitted bylight source 110 is emitted as a plurality of alternating light pulsesof different wavelengths.

Light source 110 is controlled by controller 112, which may beimplemented by any suitable computing device (e.g., processor 108),integrated circuit, and/or combination of hardware and/or software asmay serve a particular implementation. In some examples, controller 112is configured to control light source 110 by turning light source 110 onand off and/or setting an intensity of light generated by light source110. Controller 112 may be manually operated by a user, or may beprogrammed to control light source 110 automatically.

Light emitted by light source 110 travels via an optical conduit 114(e.g., a light pipe, a light guide, a waveguide, a single-mode opticalfiber, and/or or a multi-mode optical fiber) to body 102 of a subject.Body 102 may include any suitable turbid medium. For example, in someimplementations, body 102 is a head or any other body part of a human orother animal. Alternatively, body 102 may be a non-living object. Forillustrative purposes, it will be assumed in the examples providedherein that body 102 is a human head.

As indicated by arrow 120, the light emitted by light source 110 entersbody 102 at a first location 122 on body 102. Accordingly, a distal endof optical conduit 114 may be positioned at (e.g., right above, inphysical contact with, or physically attached to) first location 122(e.g., to a scalp of the subject). In some examples, the light mayemerge from optical conduit 114 and spread out to a certain spot size onbody 102 to fall under a predetermined safety limit. At least a portionof light indicated by arrow 120 may be scattered within body 102.

As used herein, “distal” means nearer, along the optical path of thelight emitted by light source 110 or the light received by detector 104,to the target (e.g., within body 102) than to light source 110 ordetector 104. Thus, the distal end of optical conduit 114 is nearer tobody 102 than to light source 110, and the distal end of optical conduit116 is nearer to body 102 than to detector 104. Additionally, as usedherein, “proximal” means nearer, along the optical path of the lightemitted by light source 110 or the light received by detector 104, tolight source 110 or detector 104 than to body 102. Thus, the proximalend of optical conduit 114 is nearer to light source 110 than to body102, and the proximal end of optical conduit 116 is nearer to detector104 than to body 102.

As shown, the distal end of optical conduit 116 (e.g., a light pipe, alight guide, a waveguide, a single-mode optical fiber, and/or amulti-mode optical fiber) is positioned at (e.g., right above, inphysical contact with, or physically attached to) output location 126 onbody 102. In this manner, optical conduit 116 may collect at least aportion of the scattered light (indicated as light 124) as it exits body102 at location 126 and carry light 124 to detector 104. Light 124 maypass through one or more lenses and/or other optical elements (notshown) that direct light 124 onto each of the photodetectors 106included in detector 104.

Photodetectors 106 may be connected in parallel in detector 104. Anoutput of each of photodetectors 106 may be accumulated to generate anaccumulated output of detector 104. Processor 108 may receive theaccumulated output and determine, based on the accumulated output, atemporal distribution of photons detected by photodetectors 106.Processor 108 may then generate, based on the temporal distribution, ahistogram representing a light pulse response of a target (e.g., tissue,blood flow, etc.) in body 102. Example embodiments of accumulatedoutputs are described herein.

FIG. 2 illustrates an exemplary detector architecture 200 that may beused in accordance with the systems and methods described herein. Asshown, architecture 200 includes a SPAD circuit 202 that implementsphotodetector 106, a control circuit 204, a time-to-digital converter(TDC) 206, and a signal processing circuit 208. Architecture 200 mayinclude additional or alternative components as may serve a particularimplementation.

In some examples, SPAD circuit 202 includes a SPAD and a fast gatingcircuit configured to operate together to detect a photon incident uponthe SPAD. As described herein, SPAD circuit 202 may generate an outputwhen SPAD circuit 202 detects a photon.

The fast gating circuit included in SPAD circuit 202 may be implementedin any suitable manner. For example, the fast gating circuit may includea capacitor that is pre-charged with a bias voltage before a command isprovided to arm the SPAD. Gating the SPAD with a capacitor instead ofwith an active voltage source, such as is done in some conventional SPADarchitectures, has a number of advantages and benefits. For example, aSPAD that is gated with a capacitor may be armed practicallyinstantaneously compared to a SPAD that is gated with an active voltagesource. This is because the capacitor is already charged with the biasvoltage when a command is provided to arm the SPAD. This is describedmore fully in U.S. Pat. Nos. 10,158,038 and 10,424,683, which areincorporated herein by reference in their entireties.

In some alternative configurations, SPAD circuit 202 does not include afast gating circuit. In these configurations, the SPAD included in SPADcircuit 202 may be gated in any suitable manner.

Control circuit 204 may be implemented by an application specificintegrated circuit (ASIC) or any other suitable circuit configured tocontrol an operation of various components within SPAD circuit 202. Forexample, control circuit 204 may output control logic that puts the SPADincluded in SPAD circuit 202 in either an armed or a disarmed state.

In some examples, control circuit 204 may control a gate delay, whichspecifies a predetermined amount of time control circuit 204 is to waitafter an occurrence of a light pulse (e.g., a laser pulse) to put theSPAD in the armed state. To this end, control circuit 204 may receivelight pulse timing information, which indicates a time at which a lightpulse occurs (e.g., a time at which the light pulse is applied to body102). Control circuit 204 may also control a programmable gate width,which specifies how long the SPAD is kept in the armed state beforebeing disarmed.

Control circuit 204 is further configured to control signal processingcircuit 208. For example, control circuit 204 may provide histogramparameters (e.g., time bins, number of light pulses, type of histogram,etc.) to signal processing circuit 208. Signal processing circuit 208may generate histogram data in accordance with the histogram parameters.In some examples, control circuit 204 is at least partially implementedby controller 112.

TDC 206 is configured to measure a time difference between an occurrenceof an output pulse generated by SPAD circuit 202 and an occurrence of alight pulse. To this end, TDC 206 may also receive the same light pulsetiming information that control circuit 204 receives. TDC 206 may beimplemented by any suitable circuitry as may serve a particularimplementation.

Signal processing circuit 208 is configured to perform one or moresignal processing operations on data output by TDC 206. For example,signal processing circuit 208 may generate histogram data based on thedata output by TDC 206 and in accordance with histogram parametersprovided by control circuit 204. To illustrate, signal processingcircuit 208 may generate, store, transmit, compress, analyze, decode,and/or otherwise process histograms based on the data output by TDC 206.In some examples, signal processing circuit 208 may provide processeddata to control circuit 204, which may use the processed data in anysuitable manner. In some examples, signal processing circuit 208 is atleast partially implemented by processor 108.

In some examples, each photodetector 106 (e.g., SPAD circuit 202) mayhave a dedicated TDC 206 associated therewith. For example, for an arrayof N photodetectors 106, there may be a corresponding array of N TDCs206. Alternatively, a single TDC 206 may be associated with multiplephotodetectors 106. Likewise, a single control circuit 204 and a singlesignal processing circuit 208 may be provided for one or more SPADcircuits 202 and/or TDCs 206.

FIG. 3 illustrates an exemplary timing diagram 300 for performing anoptical measurement operation using optical measurement system 100. Theoptical measurement operation may be performed in accordance with a timedomain-based technique, such as TD-NIRS. Optical measurement system 100may be configured to perform the optical measurement operation bydirecting light pulses (e.g., laser pulses) toward a target within abody (e.g., body 102). The light pulses may be short (e.g., 10-2000picoseconds (ps)) and repeated at a high frequency (e.g., between100,000 hertz (Hz) and 100 megahertz (MHz)). The light pulses may bescattered by the target and at least a portion of the scattered lightmay be detected by optical measurement system 100. Optical measurementsystem 100 may measure a time relative to the light pulse for eachdetected photon. By counting the number of photons detected at each timerelative to each light pulse repeated over a plurality of light pulses,optical measurement system 100 may generate a histogram that representsa light pulse response of the target (e.g., a temporal point spreadfunction (TPSF)). The terms histogram and TPSF are used interchangeablyherein to refer to a light pulse response of a target.

Timing diagram 300 shows a sequence of light pulses 302 (e.g., lightpulses 302-1 and 302-2) that may be applied to the target (e.g., tissuewithin a brain of a user, blood flow, a fluorescent material used as aprobe in a body of a user, etc.). Timing diagram 300 also shows a pulsewave 304 representing predetermined gated time windows (also referred asgated time periods) during which photodetectors 106 are gated ON todetect photons. As shown, light pulse 302-1 is applied at a time t₀. Ata time t₁, a first instance of the predetermined gated time windowbegins. Photodetectors 106 may be armed at time t₁, enablingphotodetectors 106 to detect photons scattered by the target during thepredetermined gated time window. In this example, time t₁ is set to beat a certain time after time t₀, which may minimize photons detecteddirectly from the laser pulse, before the laser pulse reaches thetarget. However, in some alternative examples, time t₁ is set to beequal to time t₀.

At a time t₂, the predetermined gated time window ends. In someexamples, photodetectors 106 may be disarmed at time t₂. In otherexamples, photodetectors 106 may be reset (e.g., disarmed and re-armed)at time t₂ or at a time subsequent to time t₂. During the predeterminedgated time window, photodetectors 106 may detect photons scattered bythe target. Photodetectors 106 may be configured to remain armed duringthe predetermined gated time window such that photodetectors 106maintain an output upon detecting a photon during the predeterminedgated time window. For example, a photodetector 106 may detect a photonat a time t₃, which is during the predetermined gated time windowbetween times t₁ and t₂. The photodetector 106 may be configured toprovide an output indicating that the photodetector 106 has detected aphoton. The photodetector 106 may be configured to continue providingthe output until time t₂, when the photodetector may be disarmed and/orreset. Optical measurement system 100 may generate an accumulated outputfrom the plurality of photodetectors. Optical measurement system 100 maysample the accumulated output to determine times at which photons aredetected by photodetectors 106 to generate a TPSF.

FIG. 4 illustrates a graph 400 of an exemplary TPSF 402 that may begenerated by optical measurement system 100 in response to a light pulse404 (which, in practice, represents a plurality of light pulses). Graph400 shows a normalized count of photons on a y-axis and time bins on anx-axis. As shown, TPSF 402 is delayed with respect to a temporaloccurrence of light pulse 404. In some examples, the number of photonsdetected in each time bin subsequent to each occurrence of light pulse404 may be aggregated (e.g., integrated) to generate TPSF 402. TPSF 402may be analyzed and/or processed in any suitable manner to determine orinfer biological (e.g., neural) activity.

Optical measurement system 100 may be implemented by or included in anysuitable device(s). For example, optical measurement system 100 may beincluded in a non-wearable device (e.g., a medical device and/orconsumer device that is placed near the head or other body part of auser to perform one or more diagnostic, imaging, and/or consumer-relatedoperations). Optical measurement system 100 may alternatively beincluded, in whole or in part, in a sub-assembly enclosure of a wearableinvasive device (e.g., an implantable medical device for brain recordingand imaging).

Alternatively, optical measurement system 100 may be included, in wholeor in part, in a non-invasive wearable device that a user may wear toperform one or more diagnostic, imaging, analytical, and/orconsumer-related operations. The non-invasive wearable device may beplaced on a user's head or other part of the user to detect neuralactivity. In some examples, such neural activity may be used to makebehavioral and mental state analysis, awareness and predictions for theuser.

Mental state described herein refers to the measured neural activityrelated to physiological brain states and/or mental brain states, e.g.,joy, excitement, relaxation, surprise, fear, stress, anxiety, sadness,anger, disgust, contempt, contentment, calmness, focus, attention,approval, creativity, positive or negative reflections/attitude onexperiences or the use of objects, etc. Further details on the methodsand systems related to a predicted brain state, behavior, preferences,or attitude of the user, and the creation, training, and use of neuromescan be found in U.S. Provisional Patent Application No. 63/047,991,filed Jul. 3, 2020. Exemplary measurement systems and methods usingbiofeedback for awareness and modulation of mental state are describedin more detail in U.S. patent application Ser. No. 16/364,338, filedMar. 26, 2019, published as US2020/0196932A1. Exemplary measurementsystems and methods used for detecting and modulating the mental stateof a user using entertainment selections, e.g., music, film/video, aredescribed in more detail in U.S. patent application Ser. No. 16/835,972,filed Mar. 31, 2020, published as US2020/0315510A1. Exemplarymeasurement systems and methods used for detecting and modulating themental state of a user using product formulation from, e.g., beverages,food, selective food/drink ingredients, fragrances, and assessment basedon product-elicited brain state measurements are described in moredetail in U.S. patent application Ser. No. 16/853,614, filed Apr. 20,2020, published as US2020/0337624A1. Exemplary measurement systems andmethods used for detecting and modulating the mental state of a userthrough awareness of priming effects are described in more detail inU.S. patent application Ser. No. 16/885,596, filed May 28, 2020,published as US2020/0390358A1. These applications and corresponding U.S.publications are incorporated herein by reference in their entirety.

FIG. 5 shows an exemplary non-invasive wearable brain interface system500 (“brain interface system 500”) that implements optical measurementsystem 100 (shown in FIG. 1). As shown, brain interface system 500includes a head-mountable component 502 configured to be attached toand/or worn on a user's head. Head-mountable component 502 may beimplemented by a cap shape that is worn on a head of a user. Alternativeimplementations of head-mountable component 502 include helmets,beanies, headbands, other hat shapes, or other forms conformable to beworn on a user's head, etc. Head-mountable component 502 may be made outof any suitable cloth, soft polymer, plastic, hard shell, and/or anyother suitable material as may serve a particular implementation.Examples of headgears used with wearable brain interface systems aredescribed below in more detail and in U.S. Pat. No. 10,340,408,incorporated herein by reference in its entirety.

Head-mountable component 502 includes a plurality of detectors 504,which may implement or be similar to detector 104, and a plurality oflight sources 506, which may be implemented by or be similar to lightsource 110. It will be recognized that in some alternative embodiments,head-mountable component 502 may include a single detector 504 and/or asingle light source 506.

Brain interface system 500 may be used for controlling an optical pathto the brain and/or for transforming photodetector measurements into anintensity value that represents an optical property of a target withinthe brain. Brain interface system 500 allows optical detection of deepanatomical locations beyond skin and bone (e.g., skull) by extractingdata from photons originating from light sources 506 and emitted to atarget location within the user's brain, in contrast to conventionalimaging systems and methods (e.g., optical coherence tomography (OCT),continuous wave near infrared spectroscopy (CW-NIRS)), which only imagesuperficial tissue structures or through optically transparentstructures.

Brain interface system 500 may further include a processor 508configured to communicate with (e.g., control and/or receive signalsfrom) detectors 504 and light sources 506 by way of a communication link510. Communication link 510 may include any suitable wired and/orwireless communication link. Processor 508 may include any suitablehousing and may be located on the user's scalp, neck, shoulders, chest,or arm, as may be desirable. In some variations, processor 508 may beintegrated in the same assembly housing as detectors 504 and lightsources 506. In some examples, processor 508 is implemented by orsimilar to processor 108 and/or controller 112.

As shown, brain interface system 500 may optionally include a remoteprocessor 512 in communication with processor 508. For example, remoteprocessor 512 may store measured data from detectors 504 and/orprocessor 508 from previous detection sessions and/or from multiplebrain interface systems (not shown). In some examples, remote processor512 is implemented by or similar to processor 108 and/or controller 112.

Power for detectors 504, light sources 506, and/or processor 508 may beprovided via a wearable battery (not shown). In some examples, processor508 and the battery may be enclosed in a single housing, and wirescarrying power signals from processor 508 and the battery may extend todetectors 504 and light sources 506. Alternatively, power may beprovided wirelessly (e.g., by induction).

In some alternative embodiments, head mountable component 502 does notinclude individual light sources. Instead, a light source configured togenerate the light that is detected by detector 504 may be includedelsewhere in brain interface system 500. For example, a light source maybe included in processor 508 and/or in another wearable or non-wearabledevice and coupled to head mountable component 502 through an opticalconnection.

Each of the light sources described herein may be implemented by anysuitable device. For example, a light source as used herein may be, forexample, a distributed feedback (DFB) laser, a super luminescent diode(SLD), a light emitting diode (LED), a diode-pumped solid-state (DPSS)laser, a laser diode (LD), a super luminescent light emitting diode(sLED), a vertical-cavity surface-emitting laser (VCSEL), a titaniumsapphire laser, a micro light emitting diode (mLED), and/or any othersuitable laser or light source.

In some alternative embodiments, head mountable component 502 does notinclude individual detectors 504. Instead, one or more detectorsconfigured to detect the scattered light from the target may be includedelsewhere in brain interface system 500. For example, a detector may beincluded in processor 508 and/or in another wearable or non-wearabledevice and coupled to head mountable component 502 through an opticalconnection.

Optical measurement system 100 may be modular in that one or morecomponents of optical measurement system 100 may be removed, changedout, or otherwise modified as may serve a particular implementation.Additionally or alternatively, optical measurement system 100 may bemodular such that one or more components of optical measurement system100 may be housed in a separate housing (e.g., module) and/or may bemovable relative to other components. Exemplary modular opticalmeasurement systems are described in more detail in U.S. ProvisionalPatent Application No. 63/081,754, filed Sep. 22, 2020, U.S. ProvisionalPatent Application No. 63/038,459, filed Jun. 12, 2020, U.S. ProvisionalPatent Application No. 63/038,468, filed Jun. 12, 2020, U.S. ProvisionalPatent Application No. 63/038,481, filed Jun. 12, 2020, and U.S.Provisional Patent Application No. 63/064,688, filed Aug. 12, 2020,which applications are incorporated herein by reference in theirrespective entireties.

As mentioned, one or more components of optical measurement system 100(e.g., head-mountable component 502) may be implemented in a wearablemodule. FIGS. 6A-7B illustrate various views of an exemplary wearablemodule 600 (“module 600”) that may implement one or more components ofoptical measurement system 100. FIG. 6A shows a perspective view of atop side of module 600, FIG. 6B shows a perspective view of a bottomside of module 600, FIG. 7A shows a plan view of the top side of module600, and FIG. 7B shows a side view of module 600. In some examples,module 600 may be included in a head-mountable component (e.g.,head-mountable component 502) of an optical measurement system (e.g.,brain interface system 500).

As shown in FIGS. 6A-7B, module 600 includes a housing 602, alight-emitting member 604, and a plurality of light-receiving members606 (e.g., light-receiving members 606-1 through 606-6). Module 600 mayinclude any additional or alternative components as may suit aparticular implementation.

Housing 602 is configured to support and/or house various components ofmodule 600, including light-emitting member 604 and light-receivingmembers 606 as well any other components of module 600 not shown inFIGS. 6A-7B (e.g., various components of a light source assembly and/ora plurality of detector assemblies, a controller, a processor, a signalprocessing circuit, etc.). As shown, housing 602 includes an upperhousing 608 and a lower housing 610 joined and held together byfasteners 612 (e.g., screws, bolts, etc.). As used herein with referenceto module 600, “upper” refers to a side of module 600 that faces atarget within a body of a user when module 600 is worn by the user, and“lower” refers to a side of module 600 that is farthest from the targetwhen module 600 is worn by the user. Light-emitting member 604 andlight-receiving members 606 protrude from an upper surface 614 (atarget-side surface) of upper housing 608 so that light may be emittedtoward and received from the target.

In some examples, as shown in FIGS. 6A, 7A, and 7B, upper housing 608includes a plurality of frame supports 616 protruding from upper surface614 and configured to support light-emitting member 604 andlight-receiving members 606 in a lateral direction. Frame supports 616may be formed integrally with upper surface 614 or may be formedseparately and attached to upper surface 614.

As shown in FIGS. 6A-7B, upper housing 608 and lower housing 610 have agenerally hexagonal shape, and are rotationally offset from one another(e.g., by about 30°). It will be recognized that upper housing 608 andlower housing 610 may alternatively be aligned with one another (ratherthan rotationally offset), and may alternatively have any other shape asmay suit a particular implementation (e.g., rectangular, square,circular, triangular, pentagonal, free-form, etc.). However, a hexagonalshape, along with beveled and/or rounded edges and corners, allows aplurality of modules to be flexibly interconnected adjacent one anotherin a wearable module assembly (e.g., in a head-mountable component).Thus, a wearable module assembly may conform to three-dimensionalsurface geometries, such as a user's head. Exemplary wearable moduleassemblies comprising a plurality of wearable modules are described inmore detail in U.S. Provisional Patent Application No. 62/992,550, filedMar. 20, 2020, which application is incorporated herein by reference inits entirety.

Light-emitting member 604 is configured to emit light (e.g., light 120,light pulses 302, or light pulse 404) from a distal end (e.g., an uppersurface) of light-emitting member 604. Light-emitting member 604 may beimplemented by any suitable optical conduit (e.g., optical conduit 114).Light-emitting member 604 is included in a light source assembly that isconfigured to generate and emit the light toward the target. In theexamples shown in FIGS. 6A-7B, the light source assembly is includedentirely within module 600. In alternative examples, one or morecomponents of the light source assembly (e.g., light source 110,controller 112, etc.) are located off module 600 and connected (e.g.,optically and/or electrically) with components in module 600 (e.g., withlight-emitting member 604, etc.). Exemplary light source assemblies thatmay be included in module 600 will be described below in more detail.

When module 600 is worn by a user, a portion of the light emitted bylight-emitting member 604 may be scattered by a target within the bodyof the user, and a portion of the scattered light (e.g., light 124) maybe received by one or more light-receiving members 606 (e.g., one ormore light-receiving light guides). Light-receiving members 606 may beimplemented by any suitable optical conduit (e.g., optical conduit 116)and/or any other suitable means for conveying light. Light-receivingmembers 606 are included in a detector assembly configured to receivethe scattered light and convey the scattered light (e.g., photons) to aphotodetector (e.g., photodetector 106). In the examples shown in FIGS.6A-7B, the detector assembly is included entirely within module 600. Inalternative examples, one or more components of the detector assembly(e.g., detector 104, photodetector 106, processor 108, control circuit204, TDC 206, signal processing circuit 208, etc.) are located offmodule 600 and connected (e.g., optically and/or electrically) withcomponents in module 600 (e.g., with light-receiving members 606).Exemplary detector assemblies that may be included in module 600 will bedescribed below in more detail.

As shown in FIG. 6B, module 600 further includes communicationinterfaces 618 on a lower surface 620 of lower housing 610.Communication interfaces 618 are configured to optically, electrically,and/or communicatively connect module 600 (e.g., components housedwithin housing 602) with other wearable modules, optical measurementsystem components (e.g., processor 508, remote processor 512, etc.),and/or any other remote components or devices (e.g., a remote computingdevice). In some examples, electrical power may be provided to module600 by way of communication interface 618. Although communicationinterfaces 618 are shown to be positioned on lower surface 620,communication interfaces 618 may additionally or alternatively bepositioned on any other surface of housing 602 as may suit a particularimplementation. Additionally or alternatively, module 600 may includeany suitable wireless communication interfaces.

FIGS. 8 and 9 illustrate a cross-sectional view of module 600, includingan exemplary light source assembly included in module 600, taken alongthe dash-dot-dash line labeled XIII-XIII shown in FIG. 7A. FIG. 8 showsan exploded view of module 600, and FIG. 9 shows a view of module 600 inan assembled state as worn by a user. As shown in FIGS. 8 and 9, module600 includes a light source assembly 802 housed within housing 602.Module 600 may also include any other suitable components that are notshown in FIGS. 8 and 9, such as one or more detector assembliesdescribed below in more detail.

In time domain-based optical measurement systems, such as systems basedon TD-NIRS, alternating short light pulses of near-infrared (NIR) lightin two or more wavelengths are emitted toward a target. A portion of theemitted light is scattered by the target while a portion of the light isabsorbed, such as by hemoglobin (Hb) and deoxygenated hemoglobin(deoxy-Hb). Differences in the absorption spectra of Hb and deoxy-Hb atdifferent wavelengths can be measured and used to determine or inferbiological activity (e.g., neural activity).

In conventional configurations of optical measurement systems, a lightsource capable of emitting light in a plurality of different wavelengthsis located away from the user so that the emitted light must be conveyedfrom the light source to the wearable module by a relatively longoptical fiber. This creates various problems. For example, the longoptical fibers apply torque and other forces to the wearable module,often causing the wearable module to move and shift around when worn bythe user. The movement of the wearable module can degrade the detectedsignal and the overall performance of the optical measurement system.Additionally, the heavy weight of the fibers can make the wearablemodule uncomfortable to wear. Furthermore, optical measurement systemsusing long fibers are large, expensive, and difficult to maintain.

To address these issues, light source assembly 802 included in module600 includes a plurality of light sources 804 (e.g., a first lightsource 804-1 and a second light source 804-2), an optical member 806,and a light guide 808. Light source assembly 802 also includes a lightguide block 810 and a spring member 812, but light guide block 810 andspring member 812 may be omitted in other embodiments. Moreover, whileFIGS. 8 and 9 show two light sources 804 and one optical member 806,light source assembly 802 may include any other suitable number of lightsources and/or optical members as may serve a particular implementation.

Each light source 804 is configured to emit light in a distinctwavelength. For example, first light source 804-1 is configured to emitfirst light 814-1 (e.g., one or more first light pulses) in a firstwavelength and second light source 804-2 is configured to emit secondlight 814-2 (e.g., one or more second light pulses) in a secondwavelength that is different from the first wavelength. The firstwavelength and the second wavelength may each be a discrete wavelengthor narrow wavelength band. For example, the first wavelength may be 750nm and the second wavelength may be 850 nm. First light source 804-1 andsecond light source 804-2 may each be implemented by any suitable lightsource described herein, such as a laser diode configured to emit thefirst wavelength and the second wavelength, respectively. In someexamples, light sources 804 may implement and/or be implemented by lightsource 110 and/or light source 506. Light sources 804 are disposed(e.g., mounted, attached, etc.) on a light source plate 816, such as butnot limited to a printed circuit board (“PCB”). Light source plate 816may be securely and immovably mounted within housing 602, such as by oneor more fasteners (e.g., screws, bolts, snap-fit, etc.).

In the example shown in FIGS. 8 and 9, light sources 804 are configuredto emit light 814 in a direction substantially parallel to a top surfaceof light sources 804 and/or light source plate 816. Accordingly, opticalmember 806 is disposed on light source plate 816 between light sources804, and light sources 804 each emit light toward optical member 806.Optical member 806 may be any one or more devices configured to redirectlight emitted from light sources 804 toward light guide 808. As shown inFIGS. 8 and 9, optical member 806 is a triangular reflecting prismconfigured to reflect light 814 at an angle of about 90°.

In alternative embodiments, optical member 806 may be a prism having anyother shape (e.g., a 3- or 4-sided pyramid), a mirror, an opticalconduit, a diffractive element, a lens, and/or any other suitableoptical device that bends or redirects light. In some examples, lightsource assembly 802 includes a plurality of optical members eachconfigured to redirect light emitted by a particular light source tolight guide 808. Additionally or alternatively, light sources 804 may beconfigured to emit light in any other direction, such as a directionnormal to an upper surface of light sources 804 and/or normal to lightsource plate 816. Accordingly, optical member 806 may be at any otherlocation to receive the emitted light, such as above light sources 804.

Light guide 808 (e.g., a light-emitting light guide) is configured toreceive light 814 from optical member 806 and emit light 814 toward atarget within a body of a user when module 600 is worn by a user. Lightguide 808 may be implemented by any suitable optical conduit describedherein. In some examples, light guide 808 implements or is implementedby optical conduit 114. As shown in FIGS. 8 and 9, light guide 808comprises a rigid, elongate waveguide. In alternative examples, lightguide 808 may comprise a bundle of optical fibers. A proximal endportion of light guide 808 is positioned nearest light sources 804 andoptical member 806 and receives light 814 from optical member 806. Adistal end portion of light guide 808 is configured to protrude fromupper surface 614 of upper housing 608 and emit light 814 toward thetarget. With this configuration, a plurality of light pulses having aplurality of different wavelengths can be emitted toward the target fromthe same location.

Light guide 808 may be supported within module 600 in any suitable way.In some examples, as shown in FIGS. 8 and 9, light guide 808 issupported by light guide block 810 and spring member 812. Light guideblock 810 may be a thick, solid member having a chamber 818 in whichlight guide 808 and spring member 812 are positioned. A proximal end ofchamber 818 opens to the exterior of module 600 through an opening 820in upper surface 614 and frame support 616. Light guide 808 ispositioned within chamber 818 such that the distal end portion of lightguide 808 is configured to protrude from upper surface 614 throughopening 820. The distal end portion of light guide 808 protrudingthrough opening 820 forms light-emitting member 604. In some examples,as shown in FIGS. 8 and 9, light guide block 810 is implemented by upperhousing 608. In alternative embodiments, light guide block 810 is formedseparately from upper housing 608 and is mounted inside upper housing608.

As shown in FIGS. 8 and 9, a support assembly 822 may be positioned overa distal end portion of light guide block 810 to hold light guide 808and spring member 812 within chamber 818. Support assembly 822 includesa first plate 824 (e.g., a lens plate of a detector assembly, describedbelow in more detail) and a second plate 826 (e.g., a detector plate ofthe detector assembly). In some examples, support assembly 822 may alsoinclude light source plate 816. First plate 824 and second plate 826include an opening 828 and an opening 830, respectively, to permit thepassage of light 814 and/or accommodate light sources 804 and opticalmember 806. In some examples, light guide block 810 includes a recessportion 832 in which first plate 824 and/or second plate 826 may bepositioned. While support assembly 822 is shown as being separate fromfirst plate 824 and second plate 826, in alternative examples lightsource plate 816 may be implemented by first plate 824 and/or secondplate 826. In additional or alternative examples, support assembly 822includes only one plate.

In some examples, light guide 808 is configured to move within chamber818 along an optical axis of light guide 808 (e.g., a longitudinaldirection of chamber 818, which is a direction extending from theproximal end of chamber 818 to the distal end of chamber 818). Thus, theextent to which the distal end portion of light guide 808 protrudes fromupper surface 614 can be adjusted in order to maintain light guide 808in physical contact with the user's body.

Spring member 812 is configured to bias the distal end portion of lightguide 808 away from upper surface 614. Thus, when module 600 is worn bya user, spring member 812 biases the distal end portion of light guide808 toward a surface of a body (e.g., skin) of the user, thereby helpingto ensure that the distal end portion of light guide 808 is in physicalcontact with the surface of the body. Spring member 812 may bias thedistal end portion of light guide 808 away from upper surface 614 in anysuitable way.

In some examples, as shown in FIGS. 8 and 9, spring member 812 comprisesa coil spring positioned around an external surface light guide 808. Aproximal end of spring member 812 pushes against first plate 824, whilethe distal end of spring member 812 pushes against a flange portion 834protruding from a portion of light guide 808. Flange portion 834 may beany suitable structure (e.g., a ring) attached to or protruding fromlight guide 808. By pressing against flange portion 834, spring member812 pushes the distal end of light guide 808 away from upper surface614. In alternative embodiments, spring member 812 may be disposed on anupper side of flange portion 834 and configured to pull flange portion834 (and hence light guide 808) toward the distal end of chamber 818.While FIGS. 8 and 9 show a coil spring, spring member 812 may beimplemented by any other suitable device or mechanism configured to biasthe distal end of light guide 808 away from upper surface 614 and towardthe user's body.

Flange portion 834 has a width (e.g., diameter) approximately equal to awidth (e.g., diameter) of chamber 818 (with sufficient tolerance toenable movement of light guide 808) to maintain a lateral position oflight guide 808 within chamber 818. Similarly, opening 820 in uppersurface 614 and frame support 616 has a width (e.g., diameter)approximately equal to a width (e.g., diameter) of light guide 808 (withsufficient tolerance to enable movement of light guide 808) to maintaina lateral position of light guide 808 within opening 820. With thisconfiguration, a proximal end of light guide 808 may be maintained inoptical alignment with optical member 806. In alternative examples,light source assembly 802 does not include spring member 812 or flangeportion 834. For instance, chamber 818 may be approximately the samewidth (e.g., diameter) as light guide 808 and light guide 808 may beimmovably attached to light guide block 810 within chamber 818.

To further maintain light guide 808 in optical alignment with opticalmember 806, as explained above, light source plate 816 is securelymounted within housing 602, thereby preventing movement of light sources804 and optical member 806 relative to light guide 808.

In some examples, light source assembly 802 may include a controller(e.g., controller 112, processor 508, etc.) configured to control lightsources 804 to output one or more light pulses. The controller may belocated in any suitable location. In some examples, the controller maybe disposed on light source plate 816, support assembly 822, or anyother suitable location within housing 602. Alternatively, thecontroller may be disposed in another device, housing, or module that isseparate from module 600 (e.g., a wearable device, a laptop computer, asmartphone, a tablet computer, etc.) and communicatively coupled withlight sources 804 by a wired or wireless communication link.

FIG. 9 shows module 600 as worn by a user. A distal end of light guide808 is in physical contact with a surface 902 of a body 904 of the user.Surface 902 presses the light guide 1004 toward upper surface 614.Spring member 812 pushes light guide 808 in the opposite direction,thereby maintaining the distal end of light guide 808 in physicalcontact with surface 902 regardless of the topography and geometry ofsurface 902, and while one or more light-receiving members protrudingfrom upper surface 614 (e.g., light-receiving members 606) are also inphysical contact with surface 902. Light 814 emitted by light sources804 enters body 904 and is scattered by a target within body 904. Atleast a portion of the scattered light returns toward module 600 and maybe received by one or more light-receiving members 606 included inmodule 600. Light-receiving members 606 may be included in one or moredetector assemblies included in module 600, as will now be described.

In the example shown in FIGS. 8 and 9, module 600 may be included in atime domain-based optical measurement system, such as a system based onTD-NIRS. In conventional configurations of an optical measurement systembased on time domain techniques, a user may wear a module that emitslight (e.g., NIR) to the user's body and collects the emitted light thathas been scattered by tissue in the body. However, in the conventionalconfigurations the detector is located away from the user so that thecollected light must be conveyed from the wearable module to thedetector by a long optical fiber. This creates several problems. First,when the wearable module is worn on a head of the user it is difficultfor the distal end of light-collecting optical fibers to penetratethrough the user's hair and maintain physical contact with the user'sskin. Second, optical measurement systems that have many detectorsrequire many optical fibers. Third, as explained above, the weight ofthe optical fibers may cause the module to move and shift around on theuser's head, thus causing motion artifacts in the detected signal.Fourth, the length of the optical fibers generates temporal dispersionin the detected signal (e.g., TPSF) because some photons of thecollected light are internally reflected many more times within the longoptical fibers than other photons due to their differentangle-of-incidence on the distal end of the optical fibers. In timedomain-based systems, the variation in the time-of-flight of photonsaffects the TPSF and masks tissue response to the emitted light.

To address these issues, module 600, when used in a time domain-basedoptical measurement system, may include a plurality of detectorassemblies, as will now be explained with reference to FIGS. 10 and 11.FIGS. 10 and 11 show a cross-sectional view of module 600, includingexemplary detector assemblies included in module 600, taken along thedashed line labeled X-X shown in FIG. 7A. FIG. 10 shows an exploded viewof module 600, and FIG. 11 shows a view of module 600 in an assembledstate as worn by a user. As shown in FIGS. 10 and 11, module 600includes a plurality of detector assemblies housed within housing 602.Module 600 may also include any other suitable components that are notshown in FIGS. 10 and 11, such as light source assembly 802 describedabove.

Each light-receiving member 606 (see FIGS. 6A-7B) in module 600 may beincluded in a distinct detector assembly 1002. FIGS. 10 and 11 showexemplary detector assemblies 1002-1, 1002-2, and 1002-3 correspondingto light-receiving members 606-1, 606-2, and 606-3, respectively.Detector assemblies corresponding to light-receiving members 606-4,606-5, and 606-6 are also included in module 600 but are not shown inthe cross-sectional view of FIGS. 10 and 11. Detector assembly 1002-1will now be described. The following description applies equally to theother detector assemblies 1002 included in module 600.

As shown, detector assembly 1002 includes a light guide 1004 and adetector 1006. Detector assembly 1002 also includes a lens system 1008,light guide block 810, a spring member 1010, and support assembly 822,but one or more of these components may be omitted in other embodiments.

Light guide 1004 is configured to receive light scattered by the target(“light 1012”) and guide light 1012 (e.g., photons) toward detector1006. Light guide 1004 may be implemented by any suitable opticalconduit described herein. As shown in FIGS. 10 and 11, light guide 1004comprises a rigid, elongate waveguide. In alternative examples, lightguide 1004 may comprise a bundle of optical fibers. In some examples,light guide 1004 implements optical conduit 116 to receive and guidelight 124. A distal end portion of light guide 1004 is configured toprotrude from upper surface 614 of upper housing 608 and receive light1012 from the target. A proximal end portion of light guide 1004 ispositioned near detector 1006 and emits light 1012 toward detector 1006.

Light guide 1004 may be supported within module 600 in any suitable way.In some examples, as shown in FIGS. 10 and 11, light guide 1004 issupported by light guide block 810 and spring member 1010. Light guideblock 810 has a chamber 1014 in which light guide 1004 and spring member1010 are positioned. A proximal end of chamber 1014 opens to theexterior of module 600 through an opening 1016 in upper surface 614 andframe support 616. Light guide 1004 is positioned within chamber 1014such that the distal end portion of light guide 1004 is configured toprotrude from upper surface 614 through opening 1016. The distal endportion of light guide 1004 protruding through opening 1016 formslight-receiving member 606-1.

In some examples, light guide 1004 is supported in a light guide blockthat is separate from light guide block 810. For example, light guide1004 may be supported in a light guide block formed separately fromupper housing 608 but that is mounted inside upper housing 608 and/orwithin another chamber (not shown) of light guide block 810.

As shown in FIGS. 10 and 11, support assembly 822 (e.g., first plate 824and/or second plate 826) may be positioned over a distal end portion oflight guide block 810 to hold light guide 1004 and spring member 1010within chamber 1014.

In some examples, light guide 1004 is configured to move within chamber1014 along an optical axis of light guide 1004 (e.g., a longitudinaldirection of chamber 1014, which is a direction extending from theproximal end of chamber 1014 to the distal end of chamber 1014). Thus,the extent to which the distal end portion of light guide 1004 protrudesfrom upper surface 614 can be adjusted in order to maintain light guide1004 in physical contact with the user's body.

Spring member 1010 is configured to bias the distal end portion of lightguide 1004 away from upper surface 614. Thus, when module 600 is worn bya user, spring member 1010 biases the distal end portion of light guide1004 toward a surface of the user's body, thereby helping to ensure thatthe distal end portion of light guide 1004 is in physical contact withthe surface of the body. Spring member 1010 may bias the distal endportion of light guide 1004 away from upper surface 614 in any suitableway.

In some examples, as shown in FIGS. 10 and 11, spring member 1010comprises a coil spring that wraps around an external surface of lightguide 1004. A proximal end of spring member 1010 pushes against firstplate 824, while the distal end of spring member 1010 pushes against aflange portion 1018 protruding from a portion of light guide 1004.Flange portion 1018 may be any suitable structure (e.g., a ring)attached to or protruding from light guide 1004. In some examples,flange portion 1018 is formed integrally with light guide 1004. Bypressing against flange portion 1018, spring member 1010 biases thedistal end of light guide 1004 away from upper surface 614. Inalternative embodiments, spring member 1010 may be disposed on an upperside of flange portion 1018 and configured to pull flange portion 1018(and hence light guide 1004) toward the distal end of chamber 1014.While FIGS. 10 and 11 show a coil spring, spring member 1010 may beimplemented by any other suitable device or mechanism configured to biasthe distal end of light guide 1004 away from upper surface 614 andtoward the user's body.

Flange portion 1018 has a width (e.g., diameter) approximately equal toa width (e.g., diameter) of chamber 1014 (with sufficient tolerance toenable movement of light guide 1004) to maintain a lateral position oflight guide 1004 within chamber 1014. Similarly, opening 1016 in uppersurface 614 and frame support 616 has a width (e.g., diameter)approximately equal to a width (e.g., diameter) of light guide 1004(with sufficient tolerance to enable movement of light guide 1004) tomaintain a lateral position of light guide 1004 within opening 1016.With this configuration, a proximal end of light guide 1004 may bemaintained in optical alignment with detector 1006. In alternativeexamples, detector assembly 1002-1 does not include spring member 1010.For instance, chamber 1014 may be approximately the same width (e.g.,diameter) as light guide 1004 and light guide 1004 may be immovablyattached to light guide block 810 within chamber 1014.

To further maintain light guide 1004 in optical alignment with detector1006, detector 1006 is mounted on support assembly 822 (e.g., on firstplate 824 or second plate 826), and support assembly 822 is securely andimmovably mounted within housing 602, thereby preventing movement ofdetector 1006 relative to light guide 1004.

To eliminate a lossy interface between light guide 1004 and detector1006 while allowing light guide 1004 to move relative to detector 1006,detector assembly 1002-1 includes lens system 1008. Lens system 1008includes a first lens 1020 and a second lens 1022. First lens 1020 isconfigured to collimate light 1012 within chamber 1014. In someexamples, first lens 1020 is formed integrally with light guide 1004and/or flange portion 1018, and thus moves within chamber 1014 as lightguide 1004 moves (due to action of spring member 1010 and/or pushing bythe user's body). As shown in FIGS. 10 and 11, first lens 1020 fitsinside spring member 1010 and thus directs light through a centeropening of spring member 1010 to second lens 1022.

Second lens 1022 is configured to focus light 1012 onto detector 1006.Second lens 1022 is supported on first plate 824. Second lens 1022 maybe supported on first plate 824 in any suitable way. As shown, secondlens 1022 is positioned within a recess 1024 in first plate 824, therebymaintaining the position of second lens 1022 fixed relative to firstlens 1020. In some embodiments, first plate 824 may be transparent(e.g., formed of glass), and second lens 1022 may be affixed to firstplate 824 by a transparent adhesive. In yet other embodiments, secondlens 1022 is formed integrally with an optically transparent first plate824. Detector 1006 is mounted on second plate 826 in an optical path oflight 1012. Thus, second lens 1022 focuses light 1012 onto detector1006. With this configuration of lens system 1008, light 1012 at theproximal end of light guide 1004 is imaged onto detector 1006, therebyeliminating a lossy interface between light guide 1004 and detector1006.

Detector 1006 may be implemented by any suitable detector describedherein (e.g., detector 104, photodetector 106, etc.). In embodiments inwhich module 600 is configured for use in a time domain-based opticalmeasurement system, detector 1006 may include at least one time-resolvedsingle photon photodetector configured to detect photons from at leastone light pulse after the at least one light pulse is scattered by thetarget. In some examples, detector 1006 comprises a plurality of SPADcircuits (e.g., an array of SPAD circuits 202).

In some examples, other circuitry associated with detector 1006 may alsobe included in module 600 (e.g., housed within housing 602). Forinstance, any one or more components of detector architecture 200 (e.g.,control circuit 204, TDC 206, and/or signal processing circuit 208) maybe housed, partially or entirely, within housing 602. These componentsmay, for example, be disposed on support assembly 822 (e.g., first plate824 and/or second plate 826) and/or light source plate 816. Additionallyor alternatively, any one or more components of detector architecture200 may be housed, partially or entirely, within an additional housingof another device that is separate from but communicatively coupled withmodule 600 (e.g., with detector 1006) by a wired or wirelesscommunication link. The other device may be another wearable device or anon-wearable device.

FIG. 11 shows module 600 as worn by a user. A distal end of each lightguide 1004 (e.g., light guide 1004-1 through 1004-3) is in physicalcontact with surface 902 of body 904 of the user. Surface 902 pressesthe light guide 1004 toward upper surface 614. Spring member 1010 pusheslight guide 1004 in the opposite direction, thereby maintaining thedistal end of each light guide 1004 in physical contact with surface 902regardless of the topography and geometry of surface 902, and regardlessof movement by the user, even when light guide 808 is also in physicalcontact with surface 902. With this configuration, scattered light 1012from the target is received by light guides 1004 and directed todetector 1006. Moreover, maintaining the distal end of each light guide1004 in physical contact with surface 902 prevents ambient light fromentering light guide 1004 and corrupting the detected signal.

In the configurations just described, light guides 1004 may have a totallength of about 10 millimeters (mm) or less, about 5 mm of less, or even3 mm or less. As a result, the total distance a photon travels from thedistal end portion of light guide 1004 to detector 1006 may beapproximately 50 mm or less, 40 mm or less, or even 30 mm or less. Suchshort distances practically eliminates, or renders negligible, anytemporal dispersion in the detected signal.

FIGS. 12-17 illustrate embodiments of a wearable device 1200 thatincludes elements of the optical measurement systems described herein.In particular, the wearable devices 1200 include a plurality of modules1202, similar to wearable module 600 shown in FIGS. 6A-7B, describedherein. For example, each module 1202 includes a source (e.g.,light-emitting member 604) and a plurality of detectors (e.g.,light-receiving members 606-1 through 606-6). The source may beimplemented by one or more light sources similar to light source 110(shown in FIG. 1). Each detector may implement or be similar to detector104 (shown in FIG. 1) and may include a plurality of photodetectors. Thewearable devices 1200 may each also include a controller (e.g.,controller 112) and a processor (e.g., processor 108) and/or becommunicatively connected to a controller and processor. In general,wearable device 1200 may be implemented by any suitable headgear and/orclothing article configured to be worn by a user. The headgear and/orclothing article may include batteries, cables, and/or other peripheralsfor the components of the optical measurement systems described herein.In some examples, the headgear includes one or more modules 600.Additionally or alternatively, modules 1202 are included in orimplemented by modules 600.

FIG. 12 illustrates an embodiment of a wearable device 1200 in the formof a helmet with a handle 1204. A cable 1206 extends from the wearabledevice 1200 for attachment to a battery or hub (with components such asa processor or the like). FIG. 13 illustrates another embodiment of awearable device 1200 in the form of a helmet showing a back view. FIG.14 illustrates a third embodiment of a wearable device 1200 in the formof a helmet with the cable 1206 leading to a wearable garment 1208 (suchas a vest or partial vest) that can include a battery or a hub.Alternatively or additionally, the wearable device 1200 can include acrest 1210 or other protrusion for placement of the hub or battery.

FIG. 15 illustrates another embodiment of a wearable device 1200 in theform of a cap with a wearable garment 1208 in the form of a scarf thatmay contain or conceal a cable, battery, and/or hub. FIG. 16 illustratesadditional embodiments of a wearable device 1200 in the form of a helmetwith a one-piece scarf 1208 or two-piece scarf 1208-1. FIG. 17illustrates an embodiment of a wearable device 1200 that includes a hood1210 and a beanie 1212 which contains the modules 1202, as well as awearable garment 1208 that may contain a battery or hub.

FIG. 18 illustrates an exemplary method 1800. While FIG. 18 illustratesexemplary operations according to one embodiment, other embodiments mayomit, add to, reorder, and/or modify any of the operations shown in FIG.18. One or more of the operations shown in FIG. 18 may be performed byany system described herein (e.g., optical measurement system 100 orbrain interface system 500), any components included therein (e.g.,wearable module 600), and/or any implementation thereof.

In operation 1802, a first light source housed within a housing of awearable module emits a first light pulse toward an optical memberhoused within the housing. The first light pulse has a first wavelength.Operation 1802 may be performed in any of the ways described herein.

In operation 1804, a second light source housed within the housing emitsa second light pulse toward the optical member. The second light pulsehas a second wavelength that is different from the first wavelength.Operation 1804 may be performed in any of the ways described herein.

In operation 1806, the optical member directs the first light pulse andthe second light pulse to a proximal end of a light guide included inthe wearable module. Operation 1806 may be performed in any of the waysdescribed herein.

In operation 1808, the light guide emits, from a distal end of the lightguide, the first light pulse and the second light pulse toward a targetwithin a body of a user of the wearable module. Operation 1808 may beperformed in any of the ways described herein.

FIG. 19 illustrates an exemplary method 1900. While FIG. 19 illustratesexemplary operations according to one embodiment, other embodiments mayomit, add to, reorder, and/or modify any of the operations shown in FIG.19. One or more of the operations shown in FIG. 19 may be performed byany system described herein (e.g., optical measurement system 100 orbrain interface system 500), any components included therein (e.g.,wearable module 600), and/or any implementation thereof.

In operation 1902, a light guide included in a wearable module beingworn by a user receives photons from at least one light pulse after theat least one light pulse is scattered by a target within a body of theuser. Operation 1902 may be performed in any of the ways describedherein.

In operation 1904, the light guide guides the photons to at least onetime-resolved single photon photodetector housed within a housing of thewearable module. Operation 1904 may be performed in any of the waysdescribed herein.

In operation 1906, the at least one time-resolved single photonphotodetector detects the photons guided by the light guide. Operation1906 may be performed in any of the ways described herein.

In some examples, a non-transitory computer-readable medium storingcomputer-readable instructions may be provided in accordance with theprinciples described herein. The instructions, when executed by aprocessor of a computing device, may direct the processor and/orcomputing device to perform one or more operations, including one ormore of the operations described herein. Such instructions may be storedand/or transmitted using any of a variety of known computer-readablemedia.

A non-transitory computer-readable medium as referred to herein mayinclude any non-transitory storage medium that participates in providingdata (e.g., instructions) that may be read and/or executed by acomputing device (e.g., by a processor of a computing device). Forexample, a non-transitory computer-readable medium may include, but isnot limited to, any combination of non-volatile storage media and/orvolatile storage media. Exemplary non-volatile storage media include,but are not limited to, read-only memory, flash memory, a solid-statedrive, a magnetic storage device (e.g. a hard disk, a floppy disk,magnetic tape, etc.), ferroelectric random-access memory (“RAM”), and anoptical disc (e.g., a compact disc, a digital video disc, a Blu-raydisc, etc.). Exemplary volatile storage media include, but are notlimited to, RAM (e.g., dynamic RAM).

FIG. 20 illustrates an exemplary computing device 2000 that may bespecifically configured to perform one or more of the processesdescribed herein. Any of the systems, units, computing devices, and/orother components described herein may be implemented by computing device2000.

As shown in FIG. 20, computing device 2000 may include a communicationinterface 2002, a processor 2004, a storage device 2006, and aninput/output (“I/O”) module 2008 communicatively connected one toanother via a communication infrastructure 2010. While an exemplarycomputing device 2000 is shown in FIG. 20, the components illustrated inFIG. 20 are not intended to be limiting. Additional or alternativecomponents may be used in other embodiments. Components of computingdevice 2000 shown in FIG. 20 will now be described in additional detail.

Communication interface 2002 may be configured to communicate with oneor more computing devices. Examples of communication interface 2002include, without limitation, a wired network interface (such as anetwork interface card), a wireless network interface (such as awireless network interface card), a modem, an audio/video connection,and any other suitable interface.

Processor 2004 generally represents any type or form of processing unitcapable of processing data and/or interpreting, executing, and/ordirecting execution of one or more of the instructions, processes,and/or operations described herein. Processor 2004 may performoperations by executing computer-executable instructions 2012 (e.g., anapplication, software, code, and/or other executable data instance)stored in storage device 2006.

Storage device 2006 may include one or more data storage media, devices,or configurations and may employ any type, form, and combination of datastorage media and/or device. For example, storage device 2006 mayinclude, but is not limited to, any combination of the non-volatilemedia and/or volatile media described herein. Electronic data, includingdata described herein, may be temporarily and/or permanently stored instorage device 2006. For example, data representative ofcomputer-executable instructions 2012 configured to direct processor2004 to perform any of the operations described herein may be storedwithin storage device 2006. In some examples, data may be arranged inone or more databases residing within storage device 2006.

I/O module 2008 may include one or more I/O modules configured toreceive user input and provide user output. I/O module 2008 may includeany hardware, firmware, software, or combination thereof supportive ofinput and output capabilities. For example, I/O module 2008 may includehardware and/or software for capturing user input, including, but notlimited to, a keyboard or keypad, a touchscreen component (e.g.,touchscreen display), a receiver (e.g., an RF or infrared receiver),motion sensors, and/or one or more input buttons.

I/O module 2008 may include one or more devices for presenting output toa user, including, but not limited to, a graphics engine, a display(e.g., a display screen), one or more output drivers (e.g., displaydrivers), one or more audio speakers, and one or more audio drivers. Incertain embodiments, I/O module 2008 is configured to provide graphicaldata to a display for presentation to a user. The graphical data may berepresentative of one or more graphical user interfaces and/or any othergraphical content as may serve a particular implementation.

In the preceding description, various exemplary embodiments have beendescribed with reference to the accompanying drawings. It will, however,be evident that various modifications and changes may be made thereto,and additional embodiments may be implemented, without departing fromthe scope of the invention as set forth in the claims that follow. Forexample, certain features of one embodiment described herein may becombined with or substituted for features of another embodimentdescribed herein. The description and drawings are accordingly to beregarded in an illustrative rather than a restrictive sense.

1. An optical measurement system comprising: a wearable modulecomprising: at least one time-resolved single photon photodetectorconfigured to detect photons from at least one light pulse after the atleast one light pulse is scattered by a target within a body of a user;at least one light guide configured to receive the photons and guide thephotons to the at least one photodetector; and a housing that housesboth the at least one photodetector and at least a portion of the atleast one light guide; and a signal processing circuit configured to:determine a temporal distribution of the photons detected by the atleast one photodetector, and generate a histogram based on the temporaldistribution of the photons.
 2. The optical measurement system of claim1, wherein: the wearable module further comprises at least onetime-to-digital converter (TDC), and the at least one TDC is configuredto measure a time difference between an occurrence of a light pulse andan occurrence of an output pulse generated by the at least onephotodetector and indicating that the at least one photodetector hasdetected a photon.
 3. The optical measurement system of claim 1, whereinthe signal processing circuit is housed in the housing.
 4. The opticalmeasurement system of claim 1, further comprising an additional housingseparate from the housing, wherein the signal processing circuit ishoused in the additional housing and communicatively coupled with the atleast one photodetector by way of a wired or wireless communicationlink.
 5. The optical measurement system of claim 4, wherein theadditional housing is wearable by the user.
 6. The optical measurementsystem of claim 1, further comprising a head-mountable componentconfigured to be worn on a head of the user, wherein the wearable moduleis included in the head-mountable component.
 7. The optical measurementsystem of claim 6, wherein the head-mountable component comprises aplurality of wearable modules.
 8. The optical measurement system ofclaim 1, wherein the target comprises a brain of the user.
 9. Theoptical measurement system of claim 1, wherein the at least onephotodetector comprises a plurality of single-photon avalanche diode(SPAD) circuits.
 10. The optical measurement system of claim 1, wherein:the wearable module further comprises at least one lens at a proximalend of the at least one light guide and configured to direct the photonsto the at least one photodetector, and the at least one lens isintegrally formed with the at least one light guide.
 11. The opticalmeasurement system of claim 1, wherein: the wearable module furthercomprises a light guide block comprising at least one chamber, the atleast one light guide is disposed in the at least one chamber, and theat least one chamber maintains the at least one light guide in opticalalignment with the at least one photodetector.
 12. The opticalmeasurement system of claim 1, wherein: the wearable module furthercomprises a support assembly, the at least one photodetector is disposedon the support assembly, and the support assembly maintains the at leastone photodetector in optical alignment with the at least one lightguide.
 13. The optical measurement system of claim 1, wherein a distanceof an optical path from the photodetector to a distal end of the lightguide is less than about 50 millimeters.
 14. The optical measurementsystem of claim 1, wherein a distal end portion of the at least onelight guide protrudes from a top surface of the housing.
 15. The opticalmeasurement system of claim 14, further comprising a spring memberconfigured to bias the distal end portion of the at least one lightguide away from the top surface of the housing.
 16. The opticalmeasurement system of claim 14, wherein the at least one light guide ismovable along an optical axis of the at least one light guide.
 17. Theoptical measurement system of claim 14, wherein the at least one lightguide is configured to be pressed toward the top surface of the housingby the body of the user when the wearable module is worn by the user.18. The optical measurement system of claim 1, further comprising: afirst light source configured to emit a first light pulse in a firstwavelength; a second light source configured to emit a second lightpulse in a second wavelength that is different from the firstwavelength; a light-emitting light guide configured to guide the firstlight pulse and the second light pulse toward the target; and an opticalmember configured to receive the first light pulse from the first lightsource and the second light pulse from the second light source anddirect the first light pulse and the second light pulse to the lightguide, wherein the at least one light pulse comprises at least one ofthe first light pulse and the second light pulse.
 19. The opticalmeasurement system of claim 18, wherein the housing houses the firstlight source, the second light source, and the optical member.
 20. Theoptical measurement system of claim 18, wherein the housing furtherhouses at least a portion of the light-emitting light guide.
 21. Theoptical measurement system of claim 18, further comprising a controllerconfigured to control one or more of the first light source or thesecond light source to output the at least one light pulse.
 22. Theoptical measurement system of claim 21, wherein the controller is housedin the housing.
 23. The optical measurement system of claim 18, whereinthe first light source and the second light source each comprises alaser diode.
 24. The optical measurement system of claim 18, wherein theoptical member comprises one or more of a prism, a mirror, or anotherlight guide.
 25. The optical measurement system of claim 18, wherein:the optical member is configured to direct the first light pulse and thesecond light pulse to a proximal end of the light guide, and thelight-emitting light guide is configured to emit the first light pulseand the second light pulse from a distal end of the light guide towardthe target.
 26. The optical measurement system of claim 18, wherein adistal end portion of the light-emitting light guide protrudes from atop surface of the housing.
 27. A wearable module for use in a timedomain-based optical measurement system, the wearable module comprising:at least one time-resolved single-photon photodetector configured todetect photons from at least one light pulse after the at least onelight pulse is scattered by a target within a body, and at least onelight guide configured to receive the photons and guide the photons tothe at least one photodetector; and a housing that houses the at leastone photodetector and at least a portion of the at least one lightguide.
 28. The wearable module of claim 27, further comprising at leastone time-to-digital converter (TDC), wherein the at least one TDC isconfigured to measure a time difference between an occurrence of a lightpulse and an occurrence of an output pulse generated by the at least onephotodetector and indicating that the at least one photodetector hasdetected a photon.
 29. The wearable module of claim 27, furthercomprising a signal processing circuit configured to: determine atemporal distribution of the photons detected by the at least onephotodetector, and generate a histogram based on the temporaldistribution of the photons.
 30. The wearable module of claim 27,wherein the at least one photodetector comprises a plurality ofsingle-photon avalanche diode (SPAD) circuits. 31-42. (canceled)